The purpose of this project was to assess whether a fat or calorie restricted diet was more effective at promoting weight loss, improving eating behaviors and reducing barriers to dietary adherence. Subjects were randomly assigned to 2 treatment conditions and clinical assessments were conducted at baseline and after 6 months of intervention. 81 individuals (15 men, 66 women) were randomized into the 2 treatment conditions. Subjects were 120-140% of ideal body weight and 25-45 years old. Treatment consisted of 24 weeks of dietary fat (22-26g/day) or calorie restriction (1000-1200 cal/day) including behavior modification and exercise. Body weight change, dietary intake, eating behaviors and barriers to adherence were measured at baseline and after treatment. T-tests were used to examine baseline differences and analysis of variance was used to assess the effect of intervention on change in outcome variables. Subjects in the low calorie condition lost over twice as much weight as those in the fat restricted group (11.5kg vs. 5.1kg). Additionally, the subjects in the low calorie condition had greater improvements in eating behavior scores, enhanced feeling of wellness, a greater distaste for dietary fat and no more pronounced feelings of deprivation than those in the fat restricted condition. Long term follow-up (12 mo. post intervention) data will be analysed to assess group differences in weight maintenance, adherence, and eating behaviors. Treatment and testing was done at the CRC at UVM.